Your fizzy drink bottle and your fleece jacket are the same plastic
Call it polyester when it is woven into clothes and PET when it is moulded into bottles. Either way it is one of the world's most common plastics, with 31 million tons produced in 2025 and more than 60 percent of it spun into fibres rather than packaging.
Polyethylene terephthalate belongs to the polyester family. It is made by joining terephthalic acid, or a related compound, with ethylene glycol in a condensation reaction that gives off water or methanol, and the resulting chains can then be lengthened by further polycondensation. Recycled PET can feed the process too. It carries resin identification code 1, the number stamped on bottles to guide recycling. Depending on how it is heated and cooled it can be clear and amorphous or partly crystalline; the crystalline form stays transparent when its particles are smaller than 500 nanometres and turns opaque white when they grow to a few micrometres.
The textile story began with J. R. Whinfield, credited with inventing polyester fibre, which ICI brought to market in the 1940s as Terylene; DuPont followed with Dacron. Today most brands are Asian, and the fibre appears in cotton blends, thermal underwear, sportswear, workwear and car seats.
In packaging, PET holds still and sparkling soft drinks, but it lets oxygen and carbon dioxide seep through slowly, which limits shelf life. Beer and other oxygen-sensitive drinks therefore get bottles with an extra barrier layer sandwiched inside. Sheets can be thermoformed into trays and blister packs. Stretched in two directions, it becomes BoPET film, which can be coated with a whisper-thin layer of evaporated aluminium to become reflective, opaque and less permeable, the material of snack wrappers and space blankets. The same film backs many solar panels.
Mixed with glass fibre, PET turns into tough engineering resins moulded into appliance parts, housings and ignition components. It waterproofs undersea cables and even protects church bell ropes where they rub through the ceiling. Non-fibre PET accounts for about 6 percent of world polymer production by mass, and forecasts put total output above 40 million tons by 2031.
Source: Polyethylene terephthalate
